Various pathologies of the human spine may be treated by stabilizing and properly positioning the vertebrae and joints of the spine. Some spinal implant systems rely on one or more rods as structural support for stabilizing and properly positioning components of the spine. Vertebral anchors such as bolts, screws, and hooks are typically secured to the vertebrae for connection to the one or more rods. These vertebral anchors must be positioned at various angles relative to the one or more rods to accommodate the anatomical structure of a patient, the physiological problem being treated, and the preference of the physician. It is difficult to provide secure connections between spinal support rods and vertebral anchors at all of the various angles that may be required, especially where there are different distances between rods and bolts and where components are located at different relative heights within the patient.
In some spinal implant systems, each vertebral anchor is connected to a rod with a connector. The connector attaches to a portion of a vertebral anchor and attaches to the rod. Example spinal systems are illustrated in U.S. Pat. Nos. 6,520,962 and 6,872,209, assigned to Warsaw Orthopedic, Inc., each of which is incorporated by reference herein in its respective entirety. The '962 patent, among other features, illustrates a “taper-lock” attachment of a connector to a vertebral anchor. The taper-lock attachment includes a tapered or wedge-shaped component against which the vertebral anchor is forced to secure the vertebral anchor relative to the connector. A wedged attachment such as this may provide a secure connection and have working components that are shielded from tissues by all or part of the body of a connector, and may be advantageous in some embodiments. A variety of other wedged attachments between a spinal rod and a connector are illustrated in connectors of the Medtronic TSRH® 3Dx™ System. These wedged attachments may also provide secure connections and have working components that are shielded from tissues by all or part of a connector, and may be advantageous in some embodiments. Wedged attachment mechanisms may also provide secure attachment with less material and may consume less volume than other mechanisms in some embodiments.
The '209 patent, among other features, illustrates a connector that includes an offset from the position of a vertebral anchor along the length of a rod. The offset, as disclosed in the '209 patent and understood by those skilled in the art, may be useful in some embodiments to reduce the profile of the spinal implant system relative to other spinal structures such as, but not limited to, the facet joints. The offset may be useful in some embodiments to displace a portion of the connector away from a vertebral anchor such that a patient's facet joint may be avoided, and therefore preserved.
A need exists for improved connectors that provide a combination of two or more of the features of wedged attachment structures for one or both linear elements, such as rods or vertebral anchors, and offset attachment of linear elements.